It is known that an internal combustion engine can be started with energy stored in one or more capacitors. In such arrangements, the energy required for starting is supplied to the capacitor from a vehicle battery (with 12 volts or 24 volts). The energy from the battery is brought to a higher voltage level by means of a high-positioning DC/DC converter and stored in the capacitor(s). Such starter systems are known, for example, from SU 1,265,388 A1 (MOSC AUTOMECH), as well as from EP 0 390 398 A1 (ISUZU).
In simpler systems, the capacitor(s) lie at the same voltage level as the vehicle battery, (i.e., no high positioner is connected between the capacitor(s) and the battery). Examples of such simpler systems are offered by DE 41 35 025 A1 (MAGNETI MARELLI), and U.S. Pat. No. 5,041,776 (ISUZU). In all of the aforementioned systems, the battery is separated from the starter motor during the starting process. All of the energy used for starting is, therefore, drawn from the capacitor accumulator(s).
JP 02175350 A (ISUZU) and JP 02175351 A (ISUZU) describe simple systems of the second-named type (i.e., the simple systems that do not include a voltage converter). However, in these disclosures, the battery and the precharged capacitor are connected in parallel during the starting process, so that both energy storage devices (i.e., accumulators) contribute to the starting process.
It is also known from EP 0 403 051 A1 (ISUZU) that a capacitor used to store starting energy can be charged only up to a certain variable voltage level. This maximum voltage level depends on the temperature of the engine coolant.
In addition to the above proposals which concern the use of capacitors as accumulators for storing and supplying starting energy to an electric starter, there are also proposals for using capacitors for other applications, (for example, as accumulators for storing energy required for electrical heating). EP 0 533 037 B1 (MAGNETI MARELLI) discloses electrical catalyst heating and EP 0 420 379 B1 discloses an electrical glow unit for a diesel engine, in which the heating energy is kept ready in a capacitor.
Finally, electrical systems with a starter battery and a vehicle battery are known from WO93/11003 (BOSCH) and EP 0 688 698 A2 (BMW et al.). In these arrangements, the starter battery and vehicle battery are charged together, but are separated during the stating process. In the last-named publication, the two batteries are connected via a control unit that controls the charging process.
Known starter systems employing capacitors guarantee reliable starting, even under very cold conditions. They also permit smaller layout of the ordinary vehicle battery, which, in itself, is less suited for short-term discharging during starting.